This invention relates to a water-cooled, high-current docking plug-connector device, particularly for automatic welding equipment. The device is of the type having a plug socket component and a plug pin component for engaging with the socket component in a manner whereby the components can be rotated relative to one another, and the device having generally elastic contact elements.
Plug-connector devices of the above type, particularly as they are employed in the automobile industry for car-body construction, should take up little space. They should fulfill the demands of high availability, permit high insertion cycles and a speedy repair capability. To achieve high insertion cycles, the frictional forces of the contact elements arising during insertion and removal should not impose too great a load on the contact surfaces. The insertion and removal forces distributed over the entire pin surface should not, therefore, take on excessive values unless it is possible to reduce the frequency of insertion. Also to be taken into consideration, however, is the fact that given the high current strengths customary in practice during brief turn-on periods, the contact elements are subject to extreme loads at the points of contact with the contact pin, particularly when there are non-uniform contact surfaces and high-frequency current surges in unstably designed contact elements. This may result in excessive heating and failure of the plug-connector device.
For the above reasons, conventional plug-connector devices, even when water-cooled so as to tolerate particularly high loads, are generally unsuited to fulfill all of the indicated requirements. Either the insertion and removal forces distributed over the entire contact pin surface are too high, which affects the permissible frequency of insertion, or the contact elements are too unstable for a heavy load, and tend to lift out of position during current surges, which in turn results in excess heating and thus in the failure of the plug connectors.
Furthermore, conventional plug-connectors in water cooled equipment cannot be placed in operation without the entire current-water connection system being disconnected, which necessitates long downtimes.
For these reasons it is common practice in electrode holder conversion systems (docking devices) to position the welding transformer behind the plug-connector devices, in order to transmit relatively low primary currents through the plug-connector devices in the case of correspondingly high voltages. With this arrangement, however, the welding transformers on robot arms must be moved simultaneously by the robot systems. In addition to the heavy weights involved and the resulting loads on the robots, this solution to the problem is also highly capital-intensive, since each electrode holder must be equipped with a transformer.